This invention relates generally to a process for the isomerization of internal olefins and more specifically to a continuous process for the preparation of aluminum alkyls from internal olefins such as mixed internal hexenes or mixed internal octenes. Linear 1-olefins derived from the internal olefins can be recovered from the aluminum alkyls by back-displacement.
Linear 1-olefin compounds such as 1-hexene are useful comonomers with lower olefins to prepare polymers having improved physical properties. The 1-hexene is normally produced as a co-product of olefin production by a variety of well-known processes such as the ethylene chain growth process in which ethylene reacts with lower aluminum alkyls to form higher alkyl aluminum compounds. The higher, C.sub.4 to C.sub.30 or above, alkyl groups are then displaced from the aluminum by, for example, ethylene or 1-butene to form C.sub.4 to C.sub.30 linear 1-olefins which can be separated and recovered. Increasing demand for 1-hexene has produced a need for preparing it as the primary product. Processes for preparing olefins such as by the dehydrogenation of paraffins or the metathesis of other olefins produce mainly internal olefin products which must then be converted to 1-olefins. Asinger et al. U.S. Pat. No. 3,322,806 describe the preparation of primary alcohols from internal olefins by reacting a non-1-olefin with an aluminum lower alkyl in the presence of catalysts which are compounds of zirconium, uranium, vanadium, chromium, thorium, tungsten, and titanium. The catalyst is believed to promote the conversion of internal olefins to 1-olefins which displace the lower alkyl groups of the aluminum alkyl. The aluminum alkyl is then converted to a primary alcohol by oxidation and hydrolysis. Asinger et al. also disclose such an isomerization/displacement process to prepare alcohols in Chemische Berichte 97, pages 2515-2520 (1964). They reported that nickel compounds were inactive. Later, the thesis of Rainer Oberghaus, Technishen Hochschulle, Aachen, (1969) reported a 55 percent yield of a 1-alcohol from i-Bu.sub.2 AlR formed by reacting internal olefin and triisobutylaluminum using a nickel(II) acetylacetonate catalyst.